This invention relates to measurement of tension in a moving threadline, and more particularly to a single pin guide tensiometer.
Disclosure No. 15046, entitled "Method for Determining Bulk and Dyeability of Draw Textured Yarn" and published in the October 1976 issue of Research Disclosure, describes a testing apparatus for measuring yarn tension during drawing of a drawtexturing feed yarn. It documents that it is known that drawtension correlates empirically with yarn properties of drawtextured yarn. The apparatus described is designed to measure only drawtension and to do so only at a single preselected draw-ratio as determined by the ratio of yarn-forwarding speeds of its draw and feed rolls. Moreover, the tensiometer suggested for use (a Rothschild tensiometer) is one which (1) employs yarn guides in addition to the strain-detecting guide, thereby causing undetermined frictional forces to be included in the detected tension, and (2) is oriented such that components of both upstream and downstream yarn tensions are included in the detected tension.
There also exists a commercially available drawtension instrument known as the "Dynafil" (manufactured by Textronico). It uses stepped-driven rolls along with separator guides for both feed and draw rolls. Multiple yarn wraps on each roll system make stringup laborious and not susceptible to automated serial handling of successive samples. Moreover, its tension detector is a rather complicated lever arrangement in which the yarn under test wraps 180 degrees about a guide, thus measuring the sum of upstream and downstream tensions and providing no means for compensating for frictional forces at the guide. A variety of interchangeable rolls is provided to enable selection of a range of draw ratios. Each such change in draw ratio, however, necessitates another tedious stringup of the yarn.